1. Field of the Invention
The present invention relates to a combustion apparatus. More particularly, the present invention relates to a combustion apparatus which includes various types of industrial furnaces and boilers that have a regenerative combustion burner.
2. Description of Related Art
A single-type regenerative combustion burner is known in the art. In a single-type regenerative combustion burner, fuel and supply air are expelled into a furnace through the regenerative combustion burner and react with each other to generate burnt gas which circulates in the furnace to the regenerative combustion burner and is exhausted through the regenerative combustion burner to the atmosphere. The regenerative combustion burner has a heat storage member which retrieves and stores the heat of the burnt gas when the burnt gas passes through the heat storage member and releases the heat to the supply air when the supply air passes through the heat storage member, thereby pre-heating the supply air.
There are two methods to mount the single-type regenerative combustion burner to a furnace:
One is a method illustrated in FIG. 22, wherein fuel and supply air expelled from the burner 100 flow toward the center of the furnace 101 so that the flame 102 directly hits the workpiece disposed at the center of the furnace.
The other is a method illustrated in FIG. 23 (and disclosed in Japanese Patent Publication HEI 8-114388), wherein the direction in which fuel and supply air are expelled from the regenerative combustion burner 103 is directed such that it is tangential to the combustion chamber 104. The burner is disposed in a concave region 105 receding from the configuration of the combustion chamber so that the tip end surface 106 of the burner recedes from the general surface 107 of the furnace wall.
However, in the above-described furnaces, the burnt gas which circulated in the combustion chamber returns to the regenerative combustion burner in a direction opposed to the direction in which the fuel and supply air were expelled, resulting in the following problems:
First, a portion of the fuel gas is drawn along by the returning burnt gas causing a short passage of non-burned fuel gas from the expelled fuel to the exhaust gas, accompanied by an increase in the amount of carbon monoxide in the exhaust gas.
Second, to prevent the increase in the amount of carbon monoxide in the exhaust gas, combustion air needs to be supplied in excessive amounts. As a result, the thermal efficiency is decreased, and a local high temperature region is generated in the furnace, accompanied by an increase in the amount of NOx (nitrogen oxides) generated.
Third, to prevent a short passage of a portion of fuel from the expelled fuel to the exhaust gas, the combustion chamber needs to be increased in size so that the exhaust gas flow does not seriously affect the flow of expelled fuel. As a result, the furnace becomes large and the thermal efficiency of the furnace is decreased.